The color negative-positive photographic system relies on the exposure of a scene onto a color negative film. The exposed negative is then projected onto a negative-working color photographic paper to form, after development, the desired positive image. In order to correctly expose the photographic paper, the average density of the negative in all three color records (red, green and blue) must be measured so that the exposure time and balance between the amounts of the red, green and blue light used to expose (print) the paper can be adjusted.
The general practice in the photofinishing industry is to scan the average color density of the negative using red, green and blue filters. There is no uniform standard for these filters. Different sets of filters may read the same negative differently because of variations in the amount of light they see. In most cases, this is not a problem since the response of a printer filter set is accounted for in the calculation of the subsequent exposure of the paper. However, this method assumes that the measured red, green and blue densities of any and all negatives, as read by a particular printer system, reflect the actual color densities in each negative.
Color negative films are considered to be "printer compatible" on a particular printer, if they yield final photographic prints with acceptable color balance differences for any given scene. It is desirable in the photofinishing industry to always produce prints that are correct in color balance regardless of the type or composition of the negative film or their average neutral exposure. In order to accomplish this, it would be required that all negatives give equal response in density, as read by both the printer (using its filter set) and the photographic paper onto which the negative will be printed. It follows that it would then be necessary to have all negatives give identical density on a wavelength-by-wavelength basis through the entire exposure scale from Dmin to maximum exposure.
In practice, this does not occur. There are variations in the wavelength-by-wavelength density (spectrophotographic) response of different negatives as seen by the photofinishing trade. Negatives from different commercial sources may use entirely different couplers which have different spectrophotographic responses. In addition, couplers may undergo aggregration and other hue shifting phenomena as a function of exposure, thus causing shifts in density at any particular wavelength of the negative throughout the exposure scale. Moreover, it is common that different couplers of the same general hue but not identical hue are used in a single color record. For example, a typical layer may consist of an image coupler and an image modifier which form different dyes of the same general class. If the different dyes that are formed are not identical, then shifts in overall hue can occur as a function of exposure due to differences in activity between the various couplers. Finally, different levels of stains or unwanted sources of color can be retained, formed or introduced into the film during processing depending on the components of the film and so, different negatives will vary from each other.
Pyrazolotriazoles have been used as magenta couplers in commercially available color negative films and can offer useful photographic advantages depending on format, even though they have high pH sensitivity and complicated syntheses. The hues of the magenta dyes formed from pyrazolotriazoles are broad in terms of bandwidth, with substantial density at wavelengths from 565 to 600 nm. A typical example of a pyrazolotriazole coupler is Coupler A shown in the experimental section.
Four equivalent couplers (those that contain only hydrogen atoms at the coupling site) such as 1- phenyl-3-acylamino-5-pyrazolones have also been used as magenta couplers in commercially available color negative films and can offer useful photographic advantages depending on format, even though they suffer from low coupling efficiency and sensitivity to formaldehyde. The hues of the magenta dyes formed from 1-phenyl-3-acylamino-5-pyrazolones are broad in terms of bandwidth, with substantial density at wavelengths from 560 to 590 nm, similar to pyrazolotriazole based dyes. Typical examples of four equivalent 1-phenyl-3-acylamino-5-pyrazolones are Couplers B and D shown in the experimental section.
A particularly preferred type of two equivalent 1-phenyl-3-acylamino-5-pyrazolone magenta image coupler is the type that contains a nitrogen based heterocyclic coupling-off group as described in U.S. Pat. Nos. 4,241,168; 4,076,533, 4,220,470, 4,367,282, 3,617,291, 4,301,235 and U.S. Pat. No. 4,310,619. However, these 4-nitrogen heterocycle-1-phenyl-3-acylamino-5-pyrazolone couplers are extremely reactive towards oxidized developer which leads to high green Dmin and poor inhibitibility when used solely as magenta image couplers. The dyes generated from these 2-equivalent couplers are identical to those formed from the corresponding 4-equivalent couplers.
1-Phenyl-3-anilino-5-pyrazolones are also used as magenta couplers in commercially available color negative films and can offer useful photographic advantages such as low pH sensitivity, high coupling efficiency and ease of synthesis. However, the hues of the magenta dyes formed from 1-phenyl-3-anilino-5-pyrazolones are narrower in bandwidth than those formed from pyrazolotriazoles or 1-phenyl-3-acylamino-5-pyrazolones, with much less density at wavelengths from 565 to 600 nm. A typical example of this type of coupler is Coupler C shown in the experimental section.
Although the foregoing numbers may vary depending on the particular color developer used, for most color developers they will be within a few nanometers. In the present application, all of the wavelength measurements given are with reference to development of the element with 2-[(4-amino-3-methyl phenyl)ethylamino]ethanol, as typically used in the industry for development of negative films as in KODAK FLEXICOLOR II Process (British Journal of Photography Annual, 1988, pp 196-198). It should be noted that it is highly desirable for a magenta image dye to have its maximum absorbance at less than 560 nm in order to match the maximum green sensitivity of photographic paper. All of the coupler classes above as well as the specific couplers described in the experimental (including the hue correction couplers of the invention) give dyes that have their maximum absorbance at less than 560 nm.
Thus, negative films using each of the above types of magenta couplers can be prepared so that the red, green (measured at one wavelength, i.e. 550 nm) and blue densities are matched. Because photographic paper has a narrow peak sensitivity range of 545-555 nm and low sensitivity at greater than 565 nm, these films would appear equivalent to the paper. However, the film with the 1-phenyl-3-anilino-5-pyrazolone magenta coupler would have less density in the region of 565 to 600 nm than the others. Printers whose green filters do not significantly read densities at wavelengths greater than 565 nm would record all three films as having the same green density. Printers with green filters that read density at wavelengths longer than 565 nm, though, would measure the film containing a 1-phenyl-3-anilino-5-pyrazolone as having less green density than the others. Since the red and blue density determination by the printer are relatively independent of the magenta coupler, such a printer would not give the film containing the 1-phenyl-3-anilino-5-pyrazolone the same exposure as the films with the other magenta couplers. Thus, paper images printed from a film containing 1-phenyl-3-anilino-5-pyrazolone magenta coupler would not have the same color balance on this type of printer as films containing either of the other two types of magenta couplers. For example, commercially used printers such as KODAK Printer Models 2610 or 3510 have green filters that do not read significant amounts of density at greater than 565 nm and so are not as sensitive to magenta dye absorbance differences in the 565-600 nm range. However, other commercially available printers such as the KODAK Model 312 or Class 35 Printers, AGFA MSP Printer or the NORITSU 1001 Minilab have green filters that will also read films with these different classes of couplers as different in overall green density.
In order to get color prints with matched color balance from a wide selection of films that contain these different couplers when using printers that read significant amounts of density from 565 to 600 nm, photofinishers must either segregate the different films so that the correct calculation of the exposure for that particular film can be made, or manually adjust the color balance during the printing operation. These operations are undesirable, leading to higher operating costs, decreased printer output and increased chance of operator error.
It would be desirable to have color negative films containing 1-phenyl-3-anilino-5-pyrazolone magenta couplers or other couplers which produce a magenta image dye with low density in the 565 to 600 nm range, which can be printed in different printers without segregating them from other films or manually adjusting color balance, and still obtain paper prints with good color balance.
Both U.S. Patent application Ser. No. 08/075,068, now U.S. Pat. No. 5,455,150, and U.S. Pat. No. 5,238,797 describe the use of photographically inert colorants or dyes with peak absorbance of 560-590 nm to improve the printer compatibility between multilayer films that contain magenta image dyes with low absorbance between 560-590 nm with film containing other types of magenta dyes. However, this improvement method is limited because the correction is not imagewise. The amount of density between 560-590 nm provided by the inert dye is fixed and constant throughout the exposure scale. At high exposures (high amounts of magenta dye), the amount of correction will be insufficient, whereas at low exposures (low amounts of magenta dye), the correction will be excessive. Only at one point in the exposure scale will the degree of correction be ideal.
U.S. Patent application Ser. No 08/139,238, now U.S. Pat. No. 5,447,831, filed Oct. 19, 1993 describes the use of a hue correction coupler which gives a dye after development with maximum absorbance &gt;560 nm to improve printer compatiblity. Such couplers have the advantage of providing imagewise correction. However, such hue correction couplers also cause some increases in the unwanted red density of the magenta layer and often have insufficent coupling activity to cause the desired degree of correction without degrading other properties of the film such as latitude and process sensitivity.
Japanese Application (Kokai) 63-61247 describes the use of polymeric two equivalent 4-nitrogen heterocycle-1-phenyl-3-acylamino-5-pyrazolone couplers together with 4-thio-1-phenyl-3-anilino-5-pyrazolone couplers in all green sensitive layers without regard to relative light sensitivity of the layer. As elsewhere described, inclusion of the hue correction coupler in the more sensitive layers distorts the desired effect of image modifying development inhibitor couplers because the hue correction coupler is so fast acting that its extent of coupling is extremely difficult to inhibit.
EP Application 0 584 793 A1 describes certain pyrazolotriazole magenta image couplers which are deficient in printer compatibility. The EP application suggests certain types of pyrazolotriazole magenta image couplers as image couplers which have a nucleus which is better in this respect.
A problem to be solved is to provide a photographic element which although it employs a magenta image dye-forming coupler which coupler is defficient in density at greater than 565 nm, the element exhibits improved green record printer compatibility without sacrificing developer process sensitivity or latitude.